This proposal will continue the development of a high resolution real time volumetric imaging (RTVI) system. Recent clinical experience with current RTVI supports its strong potential for noninvasive evaluation of the myocardium and cardiac function. Ventricular volumes and mass can be obtained on a beat-to-beat basis without geometric assumptions. RTVI improves accuracy of stress echo for early detection of perfusion deficits, reduces patient examination time, and eliminates pediatric sedation for scanning. Improvements in image quality and field of view are essential in fully exploiting the benefits of RTVI. Significant progress has been made towards the implementation of a 64:1 parallel processed scanner featuring up to 512 individual transmit and receive channels which will lead to improved image quality. Data acquisition rates have been increased by transmitting multiple ultrasound beams from the same aperture in rapid succession. This research could have major importance in overcoming reduced echo sensitivities in RTVI. The project continues on the hypothesis that using 2D arrays, multiple beam transmissions, and receive parallel processing can be effectively implemented to improve the resolution, field of view, dynamic range, and sensitivity of real time volumetric images. This renewal application proposes to complete construction and testing of the novel high resolution real time scanner and compare its performance with current scanners (2D and 3D). It proposes to optimize and implement Duke's unique multi-beam transmission system for 2D arrays. This proposal also aims to develop a unique, very high speed, scan conversion system capable of on line rendering of volumetric data for improved visualization and anatomical identification. To further improve resolution and image quality, this proposal will develop novel specialized IC's near the transducer to permit the use of over 1000 active elements without further increase in cable size. Once this barrier is eliminated, the team will implement the necessary hardware to increase receiver count to over 1000 channels.